i have had an exhaust leak for a while, pretty subtle. the strange thing is, it is more noticeable in the summer, and seems to be tied to the cabin temp controller. when set for full heat i don't notice the smell, when set for full cold i notice it more. definitely more noticeable when the sunroof is in the tilt position or if one of the windows is cracked. had the EGR cooler replaced last summer, that helped a bit as it was leaking oil on the block.

replaced turbo winter 2013/14

muffler is de-laminating, but seems in-tacked (any suggestion to completely verify it's not leaking would be a bonus)

had some body work done, tail gate and rear 1/4 panels, the dealer claims the cabin vents are fully in-tacked and shouldn't be sucking air in. it all seems to have started here, but no smoking gun.

been going on for a while getting pretty sick of it. got to be fixed or scrapped.

I know on mine, there is a center support on the exhaust pipe, about dead center of the car, which broke years ago, and causes a bit of a rattle. Last time I was under the car I saw evidence of an exhaust leak, which I presume is probably from that area.

Another place is the lower EGR pipe, but usually that causes a whistle, and/or power loss (as it's on the wrong side of the turbo). I have heard of the pipe off the turbo can break; I guess it's flexible or something; something in that area which can leak.

I also have the delaminating muffler. So far, I ignore it. It seems outer layers rust away, but the metal underneath is still good... so I leave it be.

It's really easy to find exhaust leaks from under the car. Problem is that's difficult.
Take it to a muffler chain for an estimate, try to get a look with the motor running.
But watch them the whole time, I've had more than one add occurance at these shops. Last one was a pin hole right top center of the upper radiator hose.
If you use a local tire shop, they can put it up in the air for you as well while performing that free tire rotation.